Tag Archives: Cenozoic

Our Archaeopteryx show has bedazzling fossils – the only Archaeopteryx skeleton in the New World, complete with clear impressions of feathers. Plus frog-mouthed pterodactyls, fast-swimming Sea Crocs, and slinky land lizards. Today we learn about the Louis Agassiz and his theories.

Louis Agassiz (1807-1873)

Paris and the Lure of Fish, 1836Agassiz grew up in Switzerland where he excelled as a student in chemistry and natural history. He went to Paris to study fish fossils under the Father of Paleontology, Baron Georges Cuvier. The geological history of fish seemed muddled at the time. Agassiz brought order to the fins and scales.

“There’s order in the way fish changed through the ages…” Agassiz concluded. He was the first to map out the long history of fish armor, fish jaws and fish tails.

1) The earliest time periods, the Paleozoic Era, most bony fish carried heavy armor in the form of thick scales covered with dense, shiny bone.

2) In the middle Periods, the Mesozoic, the armored fish became rarer and were replaced by fish with thin, flexible scales.

3) In the later Periods, the Cenozoic, thin-scaled fish took over in nearly all habitats.

4) Today, the old-fashioned thick scales persist only in a few fresh-water fish like the gar.

5) Tails changed too. The oldest bony fish had shark-like tails, with the vertebral column bending upwards to support the top of the fin. Later fish had more complicated tail bones, braced by special flanges, and the base of the tail was more symmetrical.

6) Jaws in the earliest bony fish were stiff, like the jaws of crocodiles. Later fish developed jaw bones that could swing outwards and forwards.

Discovery of the Ice AgeAs he traveled across Europe, Agassiz saw evidence of giant ice sheets that had covered the mountains and plains. According to Agassiz’s theory, New England too had been invaded by mile-high ice layers. Giant hairy elephants – woolly mammoths – had frolicked in the frigid habitats. At first, scholars harrumphed at Agassiz’s idea of a Glacial Period. But by the mid 1840’s the theory was proven beyond a reasonable doubt.

Boston 1846: Toast of the Town & the New MuseumFish and glaciers made Agassiz the most famous scientist of his time. When he came to Boston in the 1846, his lectures were so successful that the New England intellectuals wouldn’t let him leave. Poets and politicians, rich merchants and artists all helped raise funds to get Agassiz a professorship at Harvard. He repaid the support by working tirelessly to build a grand laboratory of science and education at Harvard – the Museum of Comparative Zoology. Opened in the 1859, the MCZ has been a leader in fossil studies ever since.

Design in Nature
Agassiz’s interests spread beyond fish and glaciers. He sought the Plan of Creation, the key to understanding all of Nature. Was it Evolution? No. Agassiz rejected any notion that natural processes somehow had transformed one species into another. He was a fierce exponent of the theory of Serial Creation: every species of fossil creature was created to fill its ecological role in its special geological time zone.

Darwin and AgassizThough he fought Darwin’s theories for his whole life, Agassiz’s work in fact provided support for the new views of evolution. The long trends in fish fins and scales were best explained by Natural Selection. Agassiz’s best students at Harvard went on to become strong supporters of Darwinism. Endowed faculty positions were established in Agassiz’s name. Agassiz Professorships were given to Alfred Sherwood Romer, the greatest Darwinian paleontologist of the 20 century, and to Stephen Jay Gould, the most eloquent defender of Darwin in the last thirty years.